1. Field of Invention
The present invention generally relates to a display panel, and more particularly, to a touch-sensing liquid crystal display (LCD) panel.
2. Description of Related Art
In today's information age, people are becoming more and more reliant on electronic devices. Electronic products such as notebook computers, mobile phones, personal digital assistants (PDAs), and digital walkmans are becoming indispensable in people's day-to-day life and work. The above-mentioned electronic products are all installed with a human-machine interface, and each is equipped with an internal system that automatically executes the command inputted by a user. Currently, some of the most widely used human-machine interfaces include keyboards, mice, and touch panels.
Recently, touch-sensing LCD panels have been widely applied in a variety of electronic products, such as global positioning systems (GPS), PDAs, mobile phones, hand-held PCs, and the like in order to replace the traditional input devices (e.g., keyboards and mice). With such drastic design changes, electronic devices have become more user-friendly, not to mention the space saved through eliminating the traditional input devices and the ease of data browsing afforded by larger display panels.
Currently, the touch-sensing LCD panel can be generally categorized into a resistive touch-sensing LCD panel and a capacitive touch-sensing LCD panel based on its driving manner and structural design. A resistive touch-sensing LCD panel is formed by a flexible top substrate, a rigid bottom substrate, and an insulating spacer. The inside surfaces of the top substrate and the bottom substrate are coated with transparent indium tin oxide films (ITO films) in order to form an upper resistive layer and a lower resistive layer.
When a finger or an object is pressed against the top substrate having the upper resistive layer, the upper resistive layer and the lower resistive layer forced in contact. When the upper and lower resistive layers are electrically connected, a voltage generated by a control unit on the upper resistive layer can be read from the lower resistive layer. The X and Y coordinates of the press position can be determined by the size of voltages at the upper and lower resistive layers which are detected by the control unit.
FIGS. 1A and 1B are respective schematic views of a conventional resistive touch-sensing LCD panel before and after touch by a user. The left-hand side of FIGS. 1A and 1B are respective frontal views of the conventional touch-sensing LCD panel, while on the right-hand side of FIGS. 1A and 1B are cross-sectional schematic views along an A-A′ line of the touch-sensing LCD panel on the left-hand side of the figures. As shown in FIG. 1A, a touch-sensing LCD panel 100 includes a bottom substrate 110, a top substrate 120, and a liquid crystal layer 130 disposed therebetween.
As shown in FIG. 1B, when the user touches the touch-sensing LCD panel 100 with a finger or an object, a cell gap between the bottom substrate 110 and the top substrate 120 is forced smaller upon application of the external pressure, thereby stressing the liquid crystal molecules of the touch area in liquid crystal layer 130. Consequently, the original alignment orientation of the liquid crystal molecules in the touch area is changed, and light leakage L is occurred.
As shown in area M depicted in FIG. 1C, when the external pressure is unavailable, a press mura can still be seen on the touch-sensing LCD panel 100. In other words, after applying an external pressure on a conventional touch-sensing LCD panel 100, the liquid crystal molecules in the liquid crystal layer 130 are affected by the surrounding distorting electric fields. Hence, the liquid crystal molecules cannot timely return to their original alignment orientation, and consequently, a press mura appears on the touch-sensing LCD panel. Ultimately, the display quality of the LCD panel is substantially deteriorated. Usually, the above-described distorting electric fields can be ascribed to the gate electric field effect from the bottom substrate, or different polarities between adjacent sub-pixels.